Extruder problems

I had problems with my i2 disconnecting randomly. My solution was to build another one. So I built an i3 rework. I had problems extruding with the i2, and now the same, if not worse with the i3. The i2 would only extrude orange hatchbox pla. Red hatchbox wouldn't work. Orange sraxxon wouldn't work. Three other filaments wouldn't work either. It's pretty much the same with the i3. The orange hatchbox is the most brittle. It breaks pretty easily, so I'm thinking it's probably the hardest too.

I have a collection of hobbed bolts. I cut a groove on the lathe, and use a tap in drill press to add hobbing.I have tried wide grooves, narrow, shallow,deep, and it doesn't seem to mattrer. I have tried loosening the tensioning bolts all the way, and cranked them down tight. I have tried Temps from 180 to 230, all with pla.

I have the same low dollar hot end on both. It's around $20 on amazon. I'm thinking that might be my problem. It seems to extrude fine when it is off the bed, and I press extrude, but during anprint, it quits extruding. Should I go with another hot end, or is there something else I should be looking at? Thanks

What exactly is the extruding problem?
PLA with bite marks from the extruder tends to get stuck on every corner on the way to the nozzle.
So maybe smoothing your cold and hotend including heatbreak will do the trick.

1.75 or 3mm filament? 3mm pla is my nemesis, if my extruders can cope with that they cope with anything. If the extruder works in free air but not during the print then it's not generating enough force on the filament. The cure depends on the failure mode - if the motor stalls then you need more torque, either more current if the motor can take it, or a bigger motor, or a larger gear ratio. If the motor chews a divot in the filament then you need more idler tension. I use very high idler tension on pla - enough to crush abs into a half round.

Obviously, however much force you apply to the filament there will be an upper limit to extrusion, so ensuring a smooth feed path, polishing the throat, using a larger nozzle diameter and checking that your extrusion mm³/s is realistic are all sensible things too.

Edited 1 time(s). Last edit at 04/09/2016 08:40AM by JamesK.

The problem is it will work for the skirt, and maybe the first layer before it just stops extruding. The motor keeps going, but nothing extrud3s. If I hit retract, and then extrude, it will work for a few more inches. It's all 1.75 pla. How should I smooth the filament path? That seems like it might work.

Edited 1 time(s). Last edit at 04/09/2016 11:40AM by Rainney.

OK, but when it stops extruding there are different possible ways it can stop, either the motors stalls, or the motor turns but the gear slips, or the gear turns and chews filament. Those are different problems with different solutions.

Edit: sorry, I appear to be having a brain fart. You said the motor keeps going, so we can assume it's chewing a hole in the filament (but it might be worth checking the gear doesn't slip - put a witness mark across the end of the shaft onto the gear and see if it stays aligned or not). Assuming the problem is chewing filament, crank up the idler tension.

And... it would help if I actually answered your question. Major problems with the throat can be fixed with a reamer. Polishing can be done with 600 grit emery paper (but it's hard to get it into the bore - the best I've managed is to roll a small piece up and present it by hand while running the lathe), followed by fine valve lapping compound on a toothpick or similar. If the bores are offset it's difficult to fix, replacing the offending part is the best option. If there is a ptfe liner then make sure it is long enough to avoid a gap where the pla is warm and soft - pla swelling into a gap in the path is one of the biggest problems. You can usually tell because the filament will jam solid and when you eventually get the filament out you can see the ring of swollen filament that filled the gap.

Edited 2 time(s). Last edit at 04/09/2016 01:29PM by JamesK.

Thanks. I'm back home and.ready to dig back into it. I have another question though. Should the filament pathway hole in the printed extruder body be the same diameter as the hole in the hot end?

I pulled the whole thing apart. There was some melted filament that leaked out above the heater block. I separated the hot end from the heatsink, and had a nice straight shot through the extruder body and the heatsink. I took the hot end apart, and polished the upper tube as good as I could.

I put it all back together, and same problem. When it was raised off the bed it would extrude forever. When i start a print, it would somehow jam up, while the motor, and both pulleys keep spinning. I switched from matter control to repetier, and it printed without a hitch. I would never guessed it was a software problem, but maybe mattercontroll was trying to feed too fast? I need to get in there, and learn the software better. Thanks for all the help. I'm going to go try some other filaments that I haven'the been able to use before.

We have a Taz5 at work which uses 3mm filament. It also has the Aleph objects version of the hexagon hot end. I can say that it takes much more force to push filament by hand though that hot end by hand than it does to push it through my hexagon or Prometheus V2 I am running at home.

We've ground a lot of filament on the Taz5 but lately it has been running smoothly. Thinking about it we changed the nozzle, with I think this one, out a few months ago and now we haven't got jamming.

With regards to your problem, which you are saying is solved, I am wondering what kind of hot end you are running. Also do you have enough cooling on the cold a part of your hot end? If you get thermal creep into the cold zone than the filament will melt early leading to high resistance and jamming.

Edited 2 time(s). Last edit at 04/13/2016 12:20AM by CTCHunter1.

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JamesK
If the motor chews a divot in the filament then you need more idler tension. I use very high idler tension on pla - enough to crush abs into a half round.

James, you may want to make a contoured idler bearing like this.

Quote
Rainney
I pulled the whole thing apart. There was some melted filament that leaked out above the heater block. I separated the hot end from the heatsink, and had a nice straight shot through the extruder body and the heatsink. I took the hot end apart, and polished the upper tube as good as I could.

I put it all back together, and same problem. When it was raised off the bed it would extrude forever. When i start a print, it would somehow jam up, while the motor, and both pulleys keep spinning. I switched from matter control to repetier, and it printed without a hitch. I would never guessed it was a software problem, but maybe mattercontroll was trying to feed too fast? I need to get in there, and learn the software better. Thanks for all the help. I'm going to go try some other filaments that I haven'the been able to use before.

Does your hot end have a PTFE tube inside? PLA is very sticky and I've heard that hot-ends without a PTFE tube jam a lot more. (I couldn't use PLA in my custom all-metal hot end)
I found a lot of good information here on the E3D troubleshooting page.

If you found that switching software helped - then the only thing I can think of is that there was different retractions, speeds, or print volume/second. That may give you a clue about the limits of your extruder/hot end combination.

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Quote
Paul Wanamaker
James, you may want to make a contoured idler bearing like this.

Hi Paul,

yes I have a couple of those, and I agree they are a good idea. Unfortunately I want these extruders to be able to handle both 1.75 and 3mm filament and I found it hard to get an idler profile other than flat to work with both diameters against a gear that also has a radius'd surface.